1. Field of the Invention
The present invention generally relates to a central heating apparatus and, more particularly, to a multi-type air heating apparatus utilizing a phase variation of a heating medium, which heats plural rooms simultaneously by utilizing the combustion heat as an exclusive heating apparatus.
2. Description of the Related Art
Conventional heating apparatuses for heating only by making use of combustion heat include, among others, an open stove for burning the fuel by using the indoor air and releasing the combustion gas into the room to heat, a forced air intake/exhaust stove for burning the fuel by using the outdoor air and releasing the combustion gas outdoors, and a forced exhaust stove for burning the fuel by using the indoor air and releasing the combustion gas outdoors.
The open stove is high in heating efficiency, and is noted for the lowest running cost if using the same fuel, and is compact in size and is portable. In this type of stove, however, since the combustion gas is released in the room, it smells for the people in the room, and the indoor air must be ventilated periodically, otherwise it may be fatal for human life due to shortage of oxygen or increase of carbon monoxide. This stove also involves the risk of inducing burns or tumbling, in a family with children, if children touch the stove unexpectedly.
By contrast, the forced air intake/exhaust stove is smaller in the risk of oxygen shortage or poisoning with carbon monoxide as experienced in the open stove because the combustion gas is discharge outdoors, but the entire size of the apparatus becomes large because combustion unit and heat exchanger are contained in the apparatus, and also the apparatus must be installed at the wall side of the room in order to extend the exhaust pipe outdoors, and therefore it is not portable and it occupies a wide space in the room, and it was particularly bothersome when it is not in use in the off-season such as a summer.
The forced exhaust stove possesses nearly the same problems as the forced air intake/exhaust stove, and as a further greater demerit, if the pressure difference between indoors and outdoors varies, for example, when exposed to a strong wind such as typhoon, the supply of air for combustion is not constant, and the combustibility is largely influenced.
Besides, when such combustion heat is used, the heating apparatus is always accompanied by the latent risk of fire because the combustion unit itself is installed indoors, and only the installed room is heated, and it was necessary to install in each room when desired to heat plural rooms at the same time.
The heating apparatus of the type of installing the combustion unit outdoors is also already available on market. One of such apparatuses is the hot water heating apparatus utilizing water as the heating medium. In this hot water heating apparatus, the hot water is heated by the combustion unit in the outdoor unit installed outdoors, and is circulated by pump, and its heat is released by the indoor radiator to heat, and its feature is that plural indoor units can be heated simultaneously by one outdoor unit. In this type of heating apparatus, however, since water is used as the heating medium, in the extremely cold district, the water in the pipe for passing the heating medium is frozen while the hbt water heating apparatus is not used and the pipe may be broken, or since the cycle in the pipe is not a closed loop, water decreases due to slight evaporation, and it is necessary to add water in the beginning of the heating season, or it is required to change the whole water if rotten, and other maintenance was required.
As other type of installing the combustion unit outdoors, a refrigerant heating air-conditioning for both heating and cooling is known. In this type, chlorofluorocarbon R-22, the refrigerant presently used in heat pump air conditioner as the heating medium when heating is directly heated and evaporated by the combustion heat, and the evaporation latent heat is conveyed into the indoor unit to heat. The radical different point is that the evaporation latent heat is used in the refrigerant heating type, while the sensible heat is used in the hot water heating apparatus.
In the conventional refrigerant heating type air conditioners, however, the fatal disadvantage is that the system is mainly designed for cooling. That is, in order to cool by using Freon, it is necessary to circulate in the freezing cycle by raising the pressure and compressing from the suction gas pressure of about 5 kg/cm.sup.2 to the discharge gas pressure of over 21 kg/cm.sup.2. Accordingly, it is required to use a compressor. Therefore, if the height or distance from the outdoor heat exchanger to the indoor heat exchanger becomes high or long, the load on the compressor increases, and a large compressor is needed. Furthermore, when the number of indoor heat exchangers for cooling and heating increases, the compressor similarly increases in size. Accordingly, the power consumption becomes larger. This is a problem always encountered when cooling or heating by the evaporation and condensation action by the compression action of the Freon refrigerant by the compressor.
Therefore, in the conventional refrigerant heating type air conditioners, since both heating and cooling actions are designed, the heating capacity is limited by the design value of the cooling capacity. In other words, the capacity of the compressor used mainly in the refrigerant heating air conditioner for household use at the present is of one horsepower class, and in the air conditioner of this class, only one room can be heated or cooled.
Besides, among the heating apparatuses for heating by installing the combustion unit indoors, the open stove has the problem of ventilation because the indoor air is contaminated, and the forced air intake/exhaust stove and forced exhaust stove occupy a wide space and are not portable. Moreover, these apparatuses give a latent anxiety about fire to the users and can heat only one room, and it was necessary to install the combustion unit in each room in order to heat plural rooms simultaneously.
In the heating apparatus using water as heating medium, it involved the problems of freezing in cold district and maintenance of water.
The aforesaid refrigerant heating type air conditioner is supplementarily described below.
The refrigerant heating air conditioner comprises, as principal constituent elements in the refrigerant heating cycle, refrigerant heater, compressor, indoor heat exchanger, outdoor heat exchanger used for cooling, expansion valve, four-way valve for changing over cooling and heating, two-way valve, and check valve. In this cycle, since the compressor can operate only in the gas state of the refrigerant, when heating, the refrigerant flows in the cycle of refrigerant heater, compressor, four-way valve, indoor heat exchanger, two-way valve and back to refrigerant heater.
Therefore, in such refrigerant heating cycle, since the refrigerant being handled is in gas form in the atmosphere of ordinary temperature and atmospheric pressure, in order to install plural indoor heat exchangers, it is required to use means for dividing the gas-form refrigerant flow, condensing in each indoor heat exchanger to return to liquid, and then converging the flows again.
In a multiple system, moreover, it is necessary to pass the refrigerant to each indoor heat exchanger at a proper flow rate suited to the required heating capacity, but it is difficult detect the flow rate, unlike water, because of the phase variation, and it is furhter difficult to pass a proper flow rate to each indoor heat exchanger. In this cycle, structurally, since the compressor is installed at the downstream side of the refrigerant heater, it is impossible to raise the temperature or pressure of the refrigerant more than the temperature or pressure resistant limit of the compressor.
Incidentally, the compressor requires lubricating oil, but the heat withstanding temperature of the oil is not so high. Therefore, it desired to set the blow-out temperature from the indoor unit higher in order to obtain a more comfortable heating, the limit was about 60.degree. C. in the existing refregerant heating air conditioner.